This invention generally relates to printer apparatus and methods of manufacture. More particularly the invention relates to a printer chassis fabricated using sheet metal members that fit together without separate fasteners or tools.
Pre-press color proofing is a procedure used by the printing industry for creating representative images of printed material. This procedure avoids the high cost and time required to produce printing plates and also avoids setting-up a high-speed, high-volume printing press to produce a representative sample of an intended image for proofing. Otherwise, in the absence of pre-press proofing, a production run may require several corrections and be reproduced several times to satisfy customer requirements. This results in lost profits. By utilizing pre-press color proofing, time and money are saved.
A laser thermal printer having half-tone color proofing capabilities is disclosed in commonly assigned U.S. Pat. No. 5,268,708 titled xe2x80x9cLaser Thermal Printer With An Automatic Material Supplyxe2x80x9d issued Dec. 7, 1993 in the name of R. Jack Harshbarger, et at. (Harshbarger, et al.) The Harshbarger, et al. device is capable of forming an image on a sheet of thermal print media by transferring dye from a roll of dye donor material to the thermal print media. This is achieved by applying a sufficient amount of thermal energy to the dye donor material to form the image on the thermal print media. This apparatus generally comprises a material supply assembly, a lathe bed scanning subsystem (which includes a lathe bed scanning frame, a translation drive, a translation stage member, a laser printhead, and a rotatable vacuum imaging drum), and exit transports for exit of thermal print media and dye donor material from the printer.
Although the printer disclosed in the Harshbarger, et al. patent performs well, there is a long-felt need to reduce manufacturing costs for this type of printer and for similar types of imaging apparatus. With respect to the lathe bed scanning frame disclosed in the Harshbarger, et al. patent, the machined casting used as the frame represents significant cost relative to the overall cost of the printer. Cost factors include the design and fabrication of the molds, the casting operation, and subsequent machining needed in order to achieve the precision necessary for a lathe bed scanning engine used in a printer of this type.
Castings present inherent problems in modeling, making it difficult to use tools such as finite element analysis to predict the suitability of a design. Moreover, due to shrinkage, porosity, and other manufacturing anomalies, it is difficult to obtain uniform results when casting multiple frames. In the assembly operation, each frame casting must be individually assessed for its suitability to manufacturing standards and must be individually machined. Further, castings also exhibit frequency response behavior, such as to resonant frequencies, which are difficult to analyze or predict. For this reason, the task of identifying and reducing vibration effects can require considerable work and experimentation. Additionally, the overall amount of time required between completion of a design and delivery of a prototype casting can be several weeks or months.
Alternative methods used for frame fabrication have been tried, with some success. For example, welded frame structures have been used. However, these welded structures require skilled welding and significant expense in manufacture.
Depending on the weight and forces exerted by supported components, a sheet metal structure, by itself, may provide sufficient support for a print engine chassis structure. However, the construction of a sheet metal chassis can require a considerable number of fasteners for assembly. This adds cost and complexity to the chassis assembly operation, adding to the total number of parts needed to build a chassis and increasing the number of manufacturing steps.
Snap-together assemblies that do not require fasteners have been utilized for electronic devices, as disclosed in U.S. Pat. No. 5,369,549 (Kopp, et al.). Kopp, et al. discloses a casing assembled without tools. However, printer chassis have been designed to use fastener hardware, which adds cost and complexity to the manufactured printer.
In summary, printer solutions have been limited to the use of conventional castings or weldments. or have employed fasteners for holding chassis parts together. As such, a printer chassis that overcomes these problems would provide numerous advantages.
An object of the present invention is to provide a sheet metal structure for a print engine chassis that can be assembled without fasteners. The goal is to provide a chassis that is structurally rigid, economical, and easy to manufacture.
With the above objects in view, the present invention provides a printer chassis for supporting an imaging drum and a printhead translation assembly, the chassis comprising a skeletal structure of interlocking rigid members that interlock without fasteners.
According to an embodiment of the present invention, sheet metal pieces are cut to form the interlocking rigid members, having spring tabs and slots that allow the interlocking rigid members to be quickly assembled by hand in order to form the skeletal structure of the printer chassis.
In another embodiment of the present invention, a spring tab to hold two structural members of a printer chassis is disclosed. The spring tab, on a first structural member, has a shoulder and a spring member which pass through a slot in a second structural member. The shoulder is pressed against one end of the slot by the spring member pressing against the other end of the slot. A hook is provided on the end of the spring tab to lock the structural members together and prevent them from being able to separate.
Also disclosed is a method for assembling a printer chassis by arranging structural members in interconnecting position relative to each other and pushing a spring tab of one structural member through a corresponding slot in another structural member to lock the structural members to each other.
A technical advantage of the present invention is a printer chassis that can be easily manufactured but is sufficiently rigid to act as a suitable replacement for a metal casting or weldment in some applications.
Another advantage of the present invention is that individual interlocking rigid members can be modified in order to change the design of the printer chassis, and even to modify the size or configuration of the overall structure. This contrasts with methods using a casting, which cannot be easily modified or scaled dimensionally.
Another advantage of the present invention is that an individual interlocking rigid member can be fabricated to allow its use with a number of different configurations. By providing alternate slot and tab features on a rigid member, a designer can allow its use in a number of different ways, as assembled. This results in potential cost savings, cutting down the number of parts that would be needed to support multiple printer configurations.